1. Field of the Invention
The present invention relates to gas analyzers. More specifically, the present invention is directed to a gas analyzer for determining the caloric content of a combustible gas.
2. Description of the Prior Art
The measurement of the BTU, or caloric, content of a combustible gas such as that supplied for home heating, etc., can provide a measure of the quality of the gas being supplied and, hence, serve as a basic for an appropriate rate or cost for the gas to be used for billing a customer who formerly was charged a rate based simply on cubic volume of gas consumption. Conventional gas analyzers for determining the composition of an unknown gas are well-known in the art. One such analyzer is known as the Orsat type and is used to absorb the constituent gases one at a time from a gas mixture and to determine the constituent gas quantities from the resulting decreases in the gas pressure. While the resulting gas analysis could be used as a basis for customer billing, such an apparatus is wholly impractical for mass installation directly in gas consumer locations. Another type of prior art gas analyzer is based on the use of thermal conductivity of the unknown gas which gas is analyzed by comparing its rate of thermal conductivity with that of a standard reference gas. Still another type of prior art gas analyzing device has used various arrangements of a catalyzing wire, e.g., platinum which has its temperature affected by the gas being burned adjacent to the wire to produce an output signal which is used to ascertain the percentage of combustible gas in the gas being tested. Still another group of prior art gas analyzers were based on an optical analysis, e.g., color, etc., of gas flame in the variety measure of combustible gas content. A recent development has used a gas flame fueled by the gas being tested to achieve a maximum flame temperature while monitoring the flow rate of the gas and air supplying the flame. All of these prior art devices have serious shortcomings in providing a rapid and accurate measure of the BTU content of the combustible gas while utilizing a compact and simple structure suitable for mass production and capable of being mounted in unattended customer locations. Accordingly, it is desirable to provide a BTU meter capable of determining the BTU or caloric content of an unknown gas composition to provide an accurate measure of the billing cost to be assigned to the gas during a sale of the gas to a consumer.